Positron beam lifetime spectroscopy at Lawrence Livermore National Laboratory

Defect analysis is needed for samples ranging in thickness from thin films to large engineering parts. We are meeting that need with two positron beam lifetime spectrometers. one on a 3 MeV electrostatic accelerator and the second on our high current linac beam. The high energy beam spectrometer performs positron lifetime analysis on thick sample specimens which can be encapsulated for containment or for in situ measurements in controlled environments. At our high current beam we are developing a low energy, microscopically focused pulsed positron beam to enable positron annihilation lifetime spectroscopy for defect specific, 3-dimensional maps with sub-micron location resolution. The data from these instruments is interpreted with the aid of first principles calculations of defect specific positron lifetimes.